Overall precipitation was well-above normal across northwest Iowa along with above normal temperatures, which made for little change to lingering areas of drought.
Every event with a place to put it; 4 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS FSD wrote it up.
Overall precipitation was well-above normal across northwest Iowa along with above normal temperatures, which made for little change to lingering areas of drought.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Sioux Falls, SD wrote its last area forecast discussion before the first event at Sep 30, 9:11 PM CST, 2 hours 49 minutes earlier.
AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 1011 PM CDT Thu Sep 30 2021 .SHORT TERM...(This Evening through Friday) Issued at 254 PM CDT Thu Sep 30 2021 Early this afternoon, radar shows a few areas of isolated showers departing northward with an additional area of scattered showers and thunderstorms developing in northeast/north central NE. A weak north- south stationary boundary remains draped just west of the I-29 corridor this afternoon, subtly warmer to the east across IA/MN where light south or east winds and warm air advection reside. High resolution models are in pretty good agreement that scattered thunderstorms will continue to develop where the sfc trough noses in along the NE/IA border late this afternoon, with this activity spreading into northwest IA heading into the evening. Tonight, a 500mb shortwave over eastern NE pivots slowly north into southeast SD amidst weak southwest flow aloft. Model guidance continues to support rain being more prevalent in two areas 1) along the MO River Valley in central SD overnight and 2) along and east of the I-29 corridor this evening where stronger warm air advection persists. In between across much of southeast SD, occasional isolated showers and storms in remnant weak forcing are possible but should see more of a drier time than wet. Despite the busier pattern, severe weather is not expected through Friday given a weak, skinny CAPE profile and very weak mid to upper level flow. Continued cloudiness will hold temperatures overnight in the 50s to lower 60s overnight. Stratus, light winds, and potential for scattered showers linger across the region on Friday amidst the stationary front with moisture pooled in the 925-850mb layer. Expect another cool day with highs only in the upper 60s to lower 70s on Friday. The aforementioned shortwave will meander into southeast SD and begins to depart the region, becoming more influenced by the more progressive northern stream southwest flow than the cutoff low over the Desert Southwest. Higher rain chances will reside in southeast SD and southwest MN on Friday where upper forcing is stronger, though scattered showers cannot be ruled out further south. Weak instability will linger north of I-90 as well, bringing potential for occasional rumbles of thunder and brief downpours. Rain should begin to taper off Friday evening from west to east as the shortwave departs. .LONG TERM...(Friday Night through Thursday) Issued at 254 PM CDT Thu Sep 30 2021 For Friday night through Saturday, the cutoff low over the Desert Southwest lifts into the Central Plains and previously split flow merges. Increasingly closer proximity to the upper trough means cloudy skies and cooler air with a mild Friday night and seasonal highs around 70 degrees Saturday. Could see lingering isolated or scattered showers Friday night through Saturday night mainly south of Interstate 90. Trimmed back NBM deterministic rain chances on the northwest edge, as they appeared broad brushed and overdone especially looking at QPF. Even the NBM 75th percentile keeps rainfall totals mainly confined to northwest IA during this period. Thus would expect a drier period than not with rainfall amounts less than a tenth of an inch. Heightened uncertainty on Sunday as an upper low tracks through, likely to our north, but most guidance would support dry conditions continuing. By Monday, we should see a bit more warming and less cloudiness as upper ridging builds into the Central U.S. from the west, developing a blocking pattern for the second half of the week. Overall expect a pleasant first half of the week with drier conditions and near to above normal temperatures generally with highs in the 70s and lows in 40s. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1008 PM CDT Thu Sep 30 2021 Scattered showers and isolated thunderstorms will continue through the night and into Friday evening. The most concentrated area will be over parts of northwest IA and southwest MN early in the period. The main threats for any of the thunderstorms will be heavy rainfall and lightning. IFR ceilings will become likely late tonight into Friday morning. These ceilings may lift a bit but a fairly widespread MVFR deck will bepossible through the day. Some fog is also possible overnight into Friday morning but confidence on this is a little lower. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && SHORT TERM...BP LONG TERM...BP AVIATION...08
Hazardous Weather Outlook National Weather Service Sioux Falls SD 421 AM CDT Thu Sep 30 2021 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-010930- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson- Pipestone-Rock-Dixon-Dakota-Beadle-Kingsbury-Brookings-Gregory- Jerauld-Sanborn-Miner-Lake-Moody-Brule-Aurora-Davison-Hanson-McCook- Minnehaha-Charles Mix-Douglas-Hutchinson-Turner-Bon Homme-Yankton- Union- 421 AM CDT Thu Sep 30 2021 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa, southwest Minnesota, northeast Nebraska, central South Dakota, east central South Dakota, south central South Dakota and southeast South Dakota. .DAY ONE...Today and tonight. Isolated thunderstorms today and tonight. Severe weather is not expected, although brief heavy rainfall is possible. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. Scattered showers with isolated thunderstorms are possible Friday into the weekend. Severe weather is not expected. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The national radar mosaic for the moment the first event began.
4 drought. Local standard time, as filed.
Precipitation was nearly double normal for Sioux Rapids and Storm Lake, but temperatures were also over 4 degrees above normal, leading to maintenance of the severe (D2) drought conditions.
Precipitation was 50 percent above normal at Cherokee, but temperatures were also around 4 degrees above normal, leading to maintenance of the severe (D2) drought conditions.
Almost 3 inches of rainfall at Spencer between September 29 and October 2 allowed for severe (D2) drought conditions to ease to moderate in early October. Crop damage is an estimate from insured losses. Information provided by the United States Department of Agriculture.
From one to two inches of rainfall around Sanborn and Primghar between September 29 and October 2 allowed for severe (D2) drought conditions to ease to moderate in early October. Crop damage is an estimate from insured losses. Information provided by the United States Department of Agriculture.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2021Every state in 2021This day in weather historyWarnings in Iowa, October 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 986909, 986910, 986911, 986912.